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    <title>Document</title>
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<script>

    let arr = [
        { comment_id: 1, user_id: 43, comment_date: "04-23", comment_content: "蜡笔小新很好看!", parent_id: null },
        { comment_id: 2, user_id: 19, comment_date: "04-24", comment_content: "还不错哦!很好看", parent_id: null },
        { comment_id: 3, user_id: 17, comment_date: "04-25", comment_content: "我也感觉蜡笔小新很好看", parent_id: "1" },
        { comment_id: 4, user_id: 14, comment_date: "04-26", comment_content: "我感觉机器猫更好看一点", parent_id: "3" },
        { comment_id: 5, user_id: 13, comment_date: "04-27", comment_content: "好看,已三连!", parent_id: null },
        { comment_id: 6, user_id: 21, comment_date: "04-26", comment_content: "你是机器猫的粉丝吗", parent_id: "4" },
        { comment_id: 7, user_id: 14, comment_date: "04-27", comment_content: "是的,我是机器猫的粉丝", parent_id: "6" },
        { comment_id: 8, user_id: 23, comment_date: "04-27", comment_content: "我更喜欢白嫖!", parent_id: "5" },
        { comment_id: 9, user_id: 25, comment_date: "04-28", comment_content: "你个白嫖怪", parent_id: "8" }
    ]


    function fn(temp) {
        let arr1 = []
        for (var i = 0; i < arr.length; i++) {
            if (arr[i].parent_id == temp) {
                arr1.push(arr[i])
                arr[i].child = fn(arr[i].comment_id)
            }
        }
        return arr1
    }
    const res = fn(null)
    console.log(res);
    



// console.log(arr1);















// [
//     { comment_id: 1, user_id: 43, comment_date: "04-23", comment_content: "蜡笔小新很好看!", parent_id: null,child:[
//         { comment_id: 3, user_id: 17, comment_date: "04-25", comment_content: "我也感觉蜡笔小新很好看", parent_id: "1" ,child:[
//             { comment_id: 4, user_id: 14, comment_date: "04-26", comment_content: "我感觉机器猫更好看一点", parent_id: "3" ,child:[
//                 { comment_id: 6, user_id: 21, comment_date: "04-26", comment_content: "你是机器猫的粉丝吗", parent_id: "4" },
//             ]},
//         ]},
//     ]}
// ]
</script>

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